A Narrative Review of the Lesser Known Medications for Treatment of Restless Legs Syndrome and Pathogenetic Implications for Their Use

The complexities in the differential diagnosis of restless legs syndrome (Willis-Ekbom disease)

INTRODUCTION

We present a literature review on the clinical conundrums surrounding the differential diagnosis of restless legs syndrome (RLS, Willis-Ekbom disease), as well as conditions that can mimic RLS. An extensive literature search showed that secondary causes of RLS ranged from commonly recognized causes, such as iron deficiency anemia, to less widely noted causes, such as rheumatoid disorders and hypothyroidism. There is a controversial association with Parkinson's disease, essential tremor, and RLS, whereby RLS is proposed as a prodromal feature.

AREAS COVERED

The clinical presentation of restless legs syndrome (RLS), a highly prevalent movement disorder usually during sleep with a circadian variation. The review highlights differences between commonly established secondary causes of RLS, RLS mimics, genetic and drug-induced RLS. A flowchart presents some key features of different and overlapping secondary RLS and mimics and genetic RLS.

EXPERT OPINION

RLS is one of the commonest movement disorders and the International Restless Legs Syndrome Study Group has suggested five-point criteria for robust diagnosis of RLS. However, even in expert hands, diagnosis is accurate in about 85% and misdiagnosis, especially with 'RLS mimics,' appears to be high. There are wide variations in the way RLS can present, and this includes different types of secondary RLS as well as drug induced or genetic patterns of RLS. Secondary RLS is highly complex and can be associated with Parkinson's disease as well as prodromal stage of Parkinson and essential tremor. Other known causes of secondary RLS are many and include end-stage kidney disease as well as metabolic disorders to painful conditions such as rheumatic disorders and fibromyalgia and polyradiculopathy.

Prerequisites for self-care actions in individuals with restless legs syndrome-A deductive qualitative analysis based on the COM-B model

Restless Legs Syndrome (RLS) affects 3% of the world's population, causing tingling sensations primarily in the legs. Incorporating self-care activities could improve the management of RLS symptoms, yet knowledge about effective self-care actions is limited. This study employs the Capability, Opportunity, and Motivation-Behaviour (COM-B) model to explore self-care behaviours in individuals with RLS, as research in this area is sparse. Qualitative content analysis of interviews with 28 participants with RLS, 26 subcategories emerged, aligning with the COM-B model's components. The first part, Capability, highlighted the importance of being able to be in motion, while the second, Opportunity referred to situations where there was a lack of trust and guidance for self-care. The third part, Motivation, emphasised the importance of fixed routines of sleep, rest, and activity. These identified prerequisites can inform the development of screening instruments and patient-reported outcome measures to evaluate self-care needs and interventions for individuals with RLS.

Current and emerging pharmaceutical strategies for the treatment and management of restless legs syndrome

INTRODUCTION

Restless legs syndrome (RLS) is a sensory-motor sleep disorder that affects up to 13% of adults in the Western world and 2-4% of children. It impairs night sleep with an impact on daily performances and life quality. Thus, moderate-to-severe RLS requires pharmacological treatment.

AREAS COVERED

In the present review, which is based on PubMed searches with no time limits, the authors discuss the recommended pharmacotherapy for RLS in addition to other emerging treatment options. The authors provide coverage to the current recommendations for both adults and pediatric patients with RLS.

EXPERT OPINION

Current evidence suggests removing all causes of secondary RLS, including iron deficiency, chronic renal failure, drugs, and treating other sleep disorders that may worsen symptoms. Also, intermittent RLS should be addressed with behavioral measures and on-demand therapy. For chronic persistent RLS, α2δ calcium channel ligands are a first-line pharmacological approach, whereas dopamine agonists are associated with increased risk and should be spared. When RLS is refractory to first-line treatment, polytherapy, or opioid monotherapy should be considered. Nonetheless, some patients may not reach sustained symptom relief. Further research is needed to better understand the pathophysiology of RLS and to develop newer more effective drugs.

Quality of life among patients with restless legs syndrome: A systematic review and meta-analysis

OBJECTIVE

The primary aim was to estimate the pooled mean score of quality of life (QoL) (total, mental and physical health components) among patients with Restless Legs Syndrome (RLS). Secondary aims were to assess: (I) QoL differences for RLS vs. control groups, (II) heterogeneity and possible sources; and (III) moderating variables.

METHODS

Studies identified in PubMed, Scopus, Web of Science, and ProQuest between January 2000 and December 2022 were included. Methodological quality was assessed with Newcastle Ottawa Scale. The protocol was pre-registered (PROSPERO, CRD42023387318).

RESULTS

Twenty-seven studies (20121 participants, 12 countries) were included. The corrected pooled estimated mean score of QoL was 47.92 (27 studies, CI 95 %: 43.11 to 52.72, range 0-100, i.e., low-high QoL) and was marginally affected by publication year (increased 0.89 by each year, p = 0.12). The corrected pooled estimated mean score of the mental health component was 47.32 (17 studies, 95 % CI: 43.12 to 51.51, range 0-100) and influenced by RLS instrument (decreased with recent versions, p = 0.05). The corrected pooled estimated mean score of the physical health component was 39.08 (17 studies, 95 % CI: 33.05 to 45.10, range 0-100), with no statistically significant moderator. The pooled estimated QoL scores were statistically significantly lower in RLS patients compared to control groups with standardized mean difference (SMD) of -0.78, -0.57 and -0.50 respectively for overall QoL (24 studies), physical and mental health components (14 studies). Total QoL SMD was affected by proportion of women.

CONCLUSION

Low QoL was revealed among RLS patients, which was statistically significantly reduced compared to control groups.

Review of the role of the endogenous opioid and melanocortin systems in the restless legs syndrome

Restless legs syndrome (RLS) is responsive to opioid, dopaminergic and iron-based treatments. Receptor blocker studies in RLS patients suggest that the therapeutic efficacy of opioids is specific to the opioid receptor and mediated indirectly through the dopaminergic system. An RLS autopsy study reveals decreases in endogenous opioids, β-endorphin and perhaps Met-enkephalin in the thalamus of RLS patients. A total opioid receptor knock-out (mu, delta and kappa) and a mu-opioid receptor knock-out mouse model of RLS show circadian motor changes akin to RLS and, although both models show sensory changes, the mu-opioid receptor knock mouse shows circadian sensory changes closest to those seen in idiopathic RLS. Both models show changes in striatal dopamine, anaemia and low serum iron. However, only in the total receptor knock-out mouse do we see the decreases in serum ferritin that are normally found in RLS. There are also decreases in serum iron when wild-type mice are administered a mu-opioid receptor blocker. In addition, the mu-opioid receptor knock-out mouse also shows increases in striatal zinc paralleling similar changes in RLS. Adrenocorticotropic hormone and α-melanocyte stimulating hormone are derived from pro-opiomelanocortin as is β-endorphin. However, they cause RLS-like symptoms and periodic limb movements when injected intraventricularly into rats. These results collectively suggest that an endogenous opioid deficiency is pathogenetic to RLS and that an altered melanocortin system may be causal to RLS as well.

Aripiprazole, a Novel Option in the Management of Restless Legs Syndrome (RLS) Patients with Augmentation and/or Severe RLS Symptoms: A Report of 4 Cases

Purpose

Restless Legs Syndrome (RLS) is a sensorimotor disorder associated with an unpleasant urge to move the limbs, relieved with movement, occurring in the evenings and with prolonged rest/inactivity. Treatment with dopamine agonists is effective for up to 60-90% of affected individuals. However, augmentation, ie, the paradoxical worsening of RLS symptoms after prolonged RLS treatment, is frequently reported, typically after 3-10 years of treatment. Here, we present 4 patients with RLS who were successfully treated with dopamine agonists but later developed augmentation. A trial of aripiprazole, a dopamine receptor partial agonist (DRPA), was initiated for treatment of augmentation symptoms.

Patients and Methods

Four patients treated for RLS with dopamine agonists developed augmentation. In each instance, augmentation symptoms did not respond adequately to a variety of medications including α2δ drugs, opioids or other agents. A trial of aripiprazole was initiated for each patient, and effects were evaluated.

Results

All four patients with severe RLS and augmentation with dopamine agonists achieved symptom control with aripiprazole. Patients endorsed 90-100% efficacy with aripiprazole by subjective self-report after failures with other agents. Further evaluation with the International Restless Legs Syndrome Study Group RLS Rating Scale (IRLS-SGRS) showed that benefits (from moderate to very severe, to mild to moderate severity) were largely maintained for 1-2 years. Aripiprazole doses to control augmentation symptoms were low (1-4 mg). No significant side effects were reported.

Conclusion

Aripiprazole may have utility for augmentation in RLS. We speculate that the partial agonist and antagonist properties of aripiprazole may limit potential for dopamine hyposensitization to progress to cause augmentation. Further research is needed to see if aripiprazole and/or other DRPAs are a viable long-term treatment option for patients experiencing augmentation and/or severe RLS with dopamine agonist therapy.